Signal transducer and activator of transcription 3 (STAT3) is a member of the STAT protein family. STAT3 mediates the expression of a variety of genes in response to cell stimuli, and thus plays a key role in many cellular pr°Cesses such as cell growth and apoptosis. STAT3 is phosphorylated by receptor-ass°Ciated Janus kinases (JAK), form homo- or heterodimers, and transl°Cate to the cell nucleus where they act as transcription activators. Besides, Epidermal Growth Factor Receptor 2 (EGFR2) has been identified as an interactor of STAT3, thus a binding ELISA assay was conducted to detect the interaction of recombinant human STAT3 and recombinant human EGFR2. Briefly, STAT3 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100µL were then transferred to EGFR2-coated microtiter wells and incubated for 2h at 37°C. Wells were washed with PBST and incubated for 1h with anti-STAT3 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 3 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37°C. Finally, add 50µL stop solution to the wells and read at 450nm immediately. The binding activity of STAT3 and EGFR2 was shown in Figure 1, and this effect was in a dose dependent manner.